| Glutamate-gated chloride channels (GluCl) belong to then icotinic ligand-gated ion channel family and are thus assumed to be heteropentamers. Each subunit contains a large extracellular N-terminal domain, four transmembrane domains (TM1--TM4), and an extracellular C terminal. Caenorhabditis elegans expresses various GluCl channels formed by alpha1, alpha2, alpha3, alpha4 and beta subunits. The best understood GluCl channel is expressed in pharyngeal muscle cells where it mediates response to the M3 motor neuron. alpha2 forms this channel, probably in association with beta. The alpha2 mutant lacks M3 neurotransmission which can be rescued by pharynx-specific alpha2 expression. My results show that alpha1 and alpha3 subunits cannot substitute for alpha2. Formation of chimeric constructs of alpha1, alpha2 and alpha3 pinpoints the M1--M3 transmembrane region of alpha2 as the minimal rescuing domain. This region may therefore be important for localization or, in association with another subunit, in the formation of the active channel. |
